The present invention relates generally to the process commonly known as friction stir welding wherein heat is generated to weld the work pieces together by rotating a pin tool in the weld seam. More particularly, the invention relates to an adapter for use in friction stir welding that is suitable for use on a standard milling or other machine capable of providing rotational movement, and the adapter includes a mechanism for adjustment of the weld tool along a longitudinal axis thereof.
Friction stir welding has been known for several years and involves a process of welding component parts together using friction heat generated at a welding joint to form a plasticized region that solidifies to join work piece sections together. To perform the welding, a probe may be inserted into a joint between the work piece stations. The probe typically includes a tool pin with either a built-in shoulder or the tool pin is inserted into a chuck, which has a shoulder. The shoulder is urged against the surface of the work pieces during the welding, and the pin and shoulder typically spin together to generate heat to form the plasticized region. Either the work piece or pin/shoulder are moved so that the pin and shoulder move along the length of the weld joint, thereby welding the component parts together.
In order to produce a quality friction stir weld, various parameters must be tightly controlled. One of the parameters to control is the depth of the probe. It is known in the art to control the depth of the probe using either a position control or a load control. A position control friction stir welder merely follows preprogramed coordinates. However, a position control system can be very sensitive to the work piece set up and tolerances. Additionally, a position control system has no way to compensate for any misalignments or imperfections in the set up, and may result in weld defects.
Force control friction stir welding systems have been developed so that the penetration and weld parameters are based upon force feedback from the rotating tool. However, these types of friction stir welding systems tend to be extremely costly and may require a special machine set up.
It is, therefore, desirable to provide a friction stir welding adapter that can be mounted to a standard milling or other rotary machine without the need for providing a specialized costly machine set up. It would further be desirable if such an adapter could be provided with a force control to assist in controlling the weld quality. One friction stir welding device is disclosed in U.S. Pat. No. 5,893,507 to Ding et al., which is incorporated in its entirety herein by reference. The device in Ding et al. includes a friction stir welding tool pin that is coupled to an axially moveable dual acting piston. The tool pin and piston are located in an arbor and mounted in a spindle housing. Ding et al. discloses that the tool pin and piston are rotated by a hydraulic motor that is also located within the spindle housing. Ding et al. does not disclose attaching the friction stir welding device to a standard milling or other rotating machine.
Another friction stir welding device is disclosed in U.S. Patent Application Publication No. 2002/017963 A1 to Strombeck et al., which is incorporated in its entirety herein by reference. Strombeck et al. discloses that the device may be utilized on a robot. The device in Strombeck et al. has a built in backing member so that the work pieces need not be supported immediately beneath the weld joint. The device also includes a housing, a rotating shaft and welding pin. The rotation of the shaft is isolated from the housing by a set of bearings. The device also includes a double acting piston for use in raising and lowering the shaft. The device also includes an upper shoulder that rotates with the shaft in one embodiment and that is isolated from the rotation of the shaft in another embodiment. The component parts to be welded are placed between the upper shoulder and the backing member with the shaft aligned with the weld joint. The double acting piston controls the pressure of the shoulder and the backing member relative to the component parts held therebetween.
It is an object of the invention to provide an adapter for use in friction stir welding that may be mounted on a standard milling or other rotating machine, and which provides pressure control in an unique manner and includes an unique linkage.